ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
How hard can it be?
£79 on ebay........I'm starting to question my sanity, I cant imagine what its like inside.......especially after the Royal Mail has finished with it!
Could well turn into spares.......will be quite a task to rebuild this cabinet.
Ahh, come on. - A good cleaning and a bit of oil and it will be fine, I'm sure. Definitely a challenge.
Martin
Just saw the listing: "Showing signs of wear."- No sh*t, Sherlock!
I know......quality isn't it......I suspect I may be requiring more that a couple of tuning lamps
Craig: How hard can it be?
Nothing is hard enough for a hard-core Beoworlder
Probably much more effort would it be to repair the electronic as to clean this dirty beast and do the optics. I can remember as I got my BM4400 from Denmark, with cabinet damaged on both sides. It was not easy but I gave my best ...
Vintage Bang & Olufsen
Very nice "O" but where is your preset cover.......cant be the finished article without a replacement cover?
Craig
Graig,
Is there damage to the aluminum finishing pieces? I mean severe damage affecting the aesthetic and missing parts? I can take care of the woodwork no problem if you want to part with it.
Let me know!
Craig: Very nice "O" but where is your preset cover.......cant be the finished article without a replacement cover? Craig
Ohhh, I see Of course you are right, I have to order preset cover from Martin immediately
But than I need 7-8 pieces for all my BM3000/4000/4400. I have to ask Martin for discount
Theomaster
Well....here it is, and it doesn't dissapoint!
Looks like damp got in too from the signs of corrosion here and there
Someone has had a go at replacing the emitter resistors on the right channel, looks like they tried to wind their own!
Definitely elbow grease to invest
I Dont have the nerve to put power to this just yet, even with my newly acquired variac! will give it a good clean and take it from there.
I wouldn't trust any of those red ROE caps that may cause damage to healthy components...
Started to clean up a little to see whats going on and spotted that someone has either been into, or attempted to get into the transformer enclosure. Left the screw out too.....this is a worry.
With the above in mind I will start by disconnecting the transformer outputs and test it in isolation before I go to much further, in the absence of any sort of plan it seems a reasonable starting point.
The main rectifier looks untouched......
Removed the lid from the transformer enclosure and, as everyone knows, its a potted unit therefore there's nothing to see....it looked in good shape visually, removed the two fuses that feed the 15v rectifier and the 35v rectifier and unsoldered the big 35v rectifier A/C leads....with the variac connected through my DVM slowly fed the power into the transformer and watched the current......at 230vac it was pulling almost nothing.
Checked all three A/C outputs from the transformer and they all look good
15v
Main 35v
During this process I have discovered that the On/Off switch is faulty in a big way.......I have applied some servisol but I fear its problems may be terminal, I seem to remember reading something about these switches being beyond redemption when they fail........anyone know?
None the less boxed up the transformer and resoldered the rectifier and continued the clean up now I'm comfortable with the transformer.
During this process I have also discovered that all four darlingtons have been replaced at some point by NTE270 and NTE271's.....probably by the guy who wound his own emmiter resistors, got to admire his bottle to do that....would need a wheatstone bridge or some such device for that surely?.....Martin are these NTE's a compatible replacement?
Beomaster 4400 came with two different types of mains switch, changed in production from serialnumber 1524001.Which type is yours?
NTE produce no transistors themselves.They buy in overstock from others and rebadge it.That's not necessarily bad in itself, it's just a hint that you cannot be sure toget the exact same thing twice even if it has the same NTE designation etc., because NTE's cross-reference guideis very "large" on replacement parts, so what would've been thousands and thousands of different spec'ed types fromother producers are referenced down to not a lot more than about a hundred NTE types.
Whatever they buy in, it just gets rebadged with the nearest designation in their own numbering system.(And sold at a solid overprice if you ask me).
If the circuit is not critical and will accept "any and all" within a certain range, then NTEs willbe fine but really only if they happen to be the only choice in the drawer for the given task.Everything else would be a tighter spec'ed solution - and usually cheaper.- And less noisy.
What makes NTE transistors go noisy, I cannot say.The handling related to the rebadging, maybe.Or perhaps it's related to just one of the original brands.Difficult to say without knowing exactly what you sit with.
If the Beomaster works, let them sit.If you experience problems, instability, noise or whatever, suspect them and replace with good old TIPs.
If I can share the fruit of my researches, the original TIP (at least the ones that came in mine) were manufactured by Texas Instruments and I was able to find some locally. Motorola also manufactured the TIP but both are rare animals now. You will find them of course on eBay but at your own risk.
A suitable modern alternative can be found at Mouser and would be the BDV65B(NPN),
BDV64B(PNP) part numbers, package SOT-93
Keep the good work!
Thanks for that Jean...I think I will do as Martin suggests and see what happens when I carefully power up before replacing the NTE's.
Looking at the On/Off switch its clear that it has come under scrutiny in the past....it's even possible that this may be the reason the 4400 was abandoned previously (bit of wishfull thinking on my part, I suspect more issues lurking down the road), it does however work very intermittently and requires some "jiggling" about to pass power.
I had the same problem on few Beolabs where the switch was sticky due to the wrong lubricant used in the past. This type of switch use a spring loaded rocker mechanism and it doesn't take much to curb the spring. It requires first to clean it, I'm using SAFETY WASH from MG Chemicals to dissolve the old grease and contaminants then lubricated with Deoxit D5.
This always worked fine for me, give it a try, you never know!
Cleaned her up as far as I'm prepared to go for now, did replace the home made resistor though, just because I had what I think is a good spare, and I have had to bypass the power switch for the time being.
Hooked up the variac and very gingerly wound the power up, as half expected the overload lamp slowly started to glow.....no fault relay clicking in though, no smells of burning or of anything untoward.....checked the idle current on the right side and couldn't adjust it up or down. did the same on the left channel and got a response to my adjustments.....left looks good, wound the power down and disconnected the right channel power plug and powered up again.....overload lamp still glows, no relay even at full power from the variac......plugged in my ipad and connected a speaker.....works fine.
So right channel needs some work.....I thought it may, odd about the fault relay not clicking in though
The good news is that the last time I went through this exercise I purchased enough hardware to repair 2 channels....and only needed to replace one set, so I'm underway.
Hi Graig,
I'm jus curious to know if you found failed components in the upstream circuit on the channel where you found blown output transistors? I found two on mine on the right channel as well but all other components are testing good!?
I can't explain that other than overheating output transistors?
Thanks!
Progress has stalled a little due to a lack of high speed diodes, I thought I had a couple but must have used them on one of the BM6000 units, hopefully they will arrive today or tomorrow.......I have gone ahead and replaced all the transistors as prescribed by the great man....and a couple of resistors too, as I had some spare capacitors I have replaced them also.
I haven't tested any components as I have replaced them, I have kept them however and will look at them in time, as I have them out I prefer to put new parts back in anyway, as we know sometimes they measure up good but fail again under stress. One transistor TR217 was a replacement and not the same number as detailed in the service manual...I will check its data sheet to see if it was a good choice (seems a repair man who winds his own resistors would be quite competent) I did however fine a broken track....but I cant tell if I broke it or it was already done....fixed it anyway, time will tell.
I've also done a bit of reading up on the overload lamp issue, looks like this lamp will come on if the circuit detects distortion in one or more of the channels as well as DC fed out to the speakers....this may be the reason mine was glowing even though the fault relay wasn't energising when I powered up ?
Checked this out as a replacement for TR217 (BC558B).....looks like it should have been fine to me.
TR117/217 equivalent would the BC559B now available at Mouser. Can't find data for the FPN4889 shown here but be careful of the noise figure...
Well.....I wouldn't put this one back, I was just curious as to its suitability as an equivalent to the BC558B that I did install, if UPS come up with the goods today and drop of my diodes I will have a go at powering up again this evening ;¬)